Without limiting the scope of the invention, its background is described in connection with novel apparatus and methods for service of subsea control systems.
It is currently estimated that approximately 60% of the world's petroleum production derives from offshore operations. To meet demands, and in an environment of increased values for oil and gas, exploration and subsequent production is being undertaken in deeper and deeper waters. For example, oil and gas is now being produced off the Louisiana coast in 9,000 feet of water. These offshore efforts have required expensive specialized solutions including construction of sophisticated subsea production structures for collection and transport of oil and gas from well heads to gathering structures, hub facilities and to onshore processing refineries.
Subsea exploration and production equipment are typically operated remotely via a plurality of control conduits that convey control signals as well as operating and control fluids. The construction of subsea exploration and production equipment is time consuming and immensely expensive. Typically the functional components of subsea control systems, including subsea umbilicals, flying leads, and the subsea control modules that control production trees, completion and test trees, blowout preventors, manifolds and distribution units, are tested on the surface, or “topsides”, prior to overboarding from the construction vessel. However, the functional components of a subsea control system can be left in position for a matter of months before being connected to the other parts of the subsea control system. It is at this time that the control systems are again integrity tested, again by connection to topside testing equipment. If the control system is not up to specification when finally ready to be connected, significant and highly expensive delays are occasioned. Assessment of how the subsea control system equipment such as umbilicals react to subsea environmental and operating conditions has heretofore only been possible through hyperbaric chamber testing, modeling and theoretical predictions of the integrity of the umbilical under the conditions in which it was deployed and will be utilized. Actual subsea testing of the status and integrity of subsea control systems such as umbilicals and subsea control modules has not heretofore been available.
Furthermore, the stresses placed on subsea control systems, particularly production umbilicals, can be immense and can include permeation by seawater contaminants; extreme pressure; extreme cold; wave, seismic and mechanical movements; vibration and impact effects; chemical incompatibility with fluids and gasses; and electrical (galvanic) and chemical corrosion.
What are needed are subsea apparatus and methods able to determine the functional status and integrity of subsea control systems after initial placement as well as prior to hook-up and once they have been on position or in operation on the seabed for some period of time.